Invasive Alien Plants

What are Invasive Alien Plant Species?
Simply put…an alien species is a non-native plant or animal that is introduced to a region outside its natural area of distribution and threatens the indigenous biological diversity. The management and control of Invasive Alien Species is governed by the National Environmental Management Biodiversity Act (NEMBA).

NEMBA categorizes alien invasive species in South as follows:
Category 1a & b – Must be removed and destroyed immediately
Category 2 – May be grown with a permit subject to strict conditions
Category 3 – May not be planted

Invasive Alien Plant Species of the region

Acacia saligna

Port Jackson is native to Australia and was introduced to South Africa in the 1880’s to stabilize coastal sands along roads. With no natural enemies, a long-living seed bank and due to a lack of or insufficient management the species spread fast and aggressively throughout South Africa. The trees are resistant to fire and felling – coppicing (splitting) and re-growing rapidly afterwards and fire actually stimulates germination of the seeds giving them an advantage over other plants. Dense thickets of Port Jackson establish and drastically reduces the biodiversity in a area.

Listed under NEMBA as a Category 1A invasive alien species Port Jackson must be removed by the owner of the property on which it occurs.

In 1987, after rigorous testing, the rust fungus Uromycladium tepperianum which is extremely damaging to these trees in Australia was introduced in South Africa. The fungus prevents reduces the plants nutrients which impacts on its growth and seed production. In 2001 the weevil, Melanterius compactus was released and is being manually redistributed through the plant’s range to reduce the amount of seed produced.

Acacia cyclops

Rooikrans is an Acacia species native to Australia was introduced to the Cape Flats in South Africa around 1857 together with Port Jackson in an attempt to stabilise sand along roads.   The species has spread throughout the Western and Eastern Cape. Some Acacia species including Rooikrans excretes substances into the soil that results in unfavorable soil conditions for indigenous vegetation.

Rooikrants / Coastal Wattle is listed as Category 1B under NEMA and must be removed by the owner of the property on which the species occurs.

Echium plantagineum aka Patterson’s Curse

Echium is responsible for the large fields of bright purple that can be seen from the roads during spring and summer in the winter rainfall region.

Patterson’s Curse which was introduced to South Africa as a ornamental species has become a significant threat not only to the natural diversity but also to cultivated crops and pasture species of the area by out-competing them for space, water and sunlight. A dense population of echium can produce a seed bank of up to 30,000 seeds per square meter.

Classified as a Category 1B invasive alien species and must be removed by the land owner.

Eichhornia crassipes

The water hyacinth is a beautiful water lily is one of the most invasive aquatic weeds in South Africa.  Native to the Amazon the species was introduced to the Western Cape in the early 1900’s.

It is listed under Category 1 and must be removed and eradicated by the landowner on whose property it occurs.

Eucalyptus species

Blue gum or Eucalyptus is native to Australia of which there are several occurring in South Africa. Six species of blue gum / Eucalyptus are listed as Invasive Alien Species in terms of NEMBA namely:
Eucalyptus camaldulensis – river red gum
Eucalyptus cladocalyx – sugar gum
Eucalyptus conferruminata – spider gum
Eucalyptus diversicolor – karri
Eucalyptus grandis – saligna or rose gum
Eucalyptus tereticornis – forest red gum

According to the law, any of these listed gums growing in riparian or Protected Areas or within a listed ecosystem or ecosystem identified for conservation is listed as Category 1b, meaning they must be removed.

Thousands of honeybee colonies are used every year to pollinate important crops across South Africa.  Our deciduous fruit industry, for example, relies on bees to pollinate blossom every spring. After the blossom season is over, honeybees move into gardens, onto farms and along roadsides in search of pollen (protein) and nectar (carbohydrates) from flowering plants.    NEM:BA Invasive Species Regulations which came into effect on 1 October, 2014 acknowledges the importance of gum trees to honeybee foraging. In particular, the regulations make provisions for landowners wishing to demarcate their gum trees as ‘bee-foraging zones’.